DESCRIPTION (Applicant's abstract): Recent national news reports of incidents of extreme violence, e.g., Columbine, Atlanta shootings, have highlighted the emotional state of the perpetrator, as a precipitant to the violent act. Specifically, such incidents have suggested that negative emotional states arising from environmental stressors, e.g., peer rejection, financial difficulties, can prompt some individuals to act out violently against others not responsible for their distress. Mirroring the above, researchers in the field of human aggression have long been interested in the role of emotion in aggressive behavior. Relevant theory and data suggest that self-reported negative mood is related to greater aggressivity (Berkowitz, 1990; Geen, 1990; Almagor & Ehrlich, 1990), and that negative affect may mediate the aggression observed in those exposed to frustrating or provoking circumstances (Berkowitz, 1989, 1988). Nonetheless, only a limited number of studies have experimentally investigated the effects of negative affect on aggressivity. The limitations of existing research include reliance on negative affect manipulations, i.e., provocation, negative evaluation, that have time-limited effects on emotion, and reliance on self-report measures of negative emotionality. The present investigation will analyze the impact of manipulated negative affect, using a novel on-going aversive stimulus, on laboratory aggressive behavior. As is customary in laboratory aggression studies, a deceptive cover story will be utilized to ensure valid responses on the dependent measure (i.e., aggression). An on-line psychophysiological measure of emotion, the startle probe methodology, will be utilized to index on-going, negative affect, in accordance with theories that predict physiological and behavioral response, consistent with the emotional state of the individual. Moreover, affective individual differences, particularly traits related to emotional reactivity, will be analyzed as moderators of the emotion-aggression effect.